If you decide to plant those willow trees, do it by a body of fresh water. They need a tremendous amount of water to survive. That's why you see them by lakes or streams in nature. They have been known to have their roots penetrate heavy iron and lead water pipes in search of water. Voracious root system.
On making compost, I like horse manure also, but the only problem I've had in the past is if the compost does not get hot enough, the weed seeds do not get killed. When cows eat, they have multiple stomachs and the process of chewing their cud mashes the seeds then goes through stomachs one after the other and the digestive process renders the weed seeds non-viable.
There are a few different types of compost, just to take this further. Biological and fungal. Fungal compost is where you find mycorrhizae and other fungal threads like actinomycetes, the white stringy stuff in the compost. Could look powdery as well. This compost is excellent for trees and plants which are enhanced by mycorrhizae. Not all plants utilize it the same way.
Bacterial compost is made using manures. In the manures are the bacteria necessary to break down the organic matter into smaller particles and humates. This type of pile gets very, very hot if turned and kept moist properly. If you use this type of compost too soon, the ammonia in the urine will kill. That needs to be fully finished before using it, but fungal compost is somewhat more forgiving and I like it better, to be honest.
The compost I use does have turkey manure in it, but not the primary source of nitrogen. Primary source of nitrogen is vegetative matter. The turkey litter is used to accelerate the heating process and finish the material faster, but poultry manures are much cooler than mammals and have nowhere near the harmful bacteria found in mammal manures.
So, that all said, I hope I didn't make it more confusing than it was before. I'm mainly saying this for outdoor growers.